Romidepsin is a natural product which was isolated from Chromobacterium violaceum by Fujisawa Pharmaceuticals. See Published Japanese Patent Application Hei 7 (1995)-64872; U.S. Pat. No. 4,977,138, issued Dec. 11, 1990, each of which is incorporated herein by reference. It is a bicyclic peptide consisting of four amino acid residues (D-valine, D-cysteine, dehydrobutyrine, and L-valine) and a novel acid (3-hydroxy-7-mercapto-4-heptenoic acid). Romidepsin is a depsipeptide which contains both amide and ester bonds. In addition to the production of C. violaceum using fermentation, romidepsin can also be prepared by synthetic or semi-synthetic means. The total synthesis of romidepsin reported by Kahn et al. involves 14 steps and yields romidepsin in 18% overall yield. J. Am. Chem. Soc. 118:7237-7238, 1996. The structure of romidepsin is shown below:
Romidepsin has been shown to have anti-microbial, immunosuppressive, and anti-tumor activities. Romidepsin is currently being tested, for example, for use in treating patients with hematological malignancies (e.g., cutaneous T-cell lymphoma (CTCL), peripheral T-cell lymphoma (PTCL), multiple myeloma, etc.) and solid tumors (e.g., prostate cancer, pancreatic cancer, etc.). It is thought to act by selectively inhibiting deacetylases (e.g., histone deacetylase, tubulin deacetylase), promising new targets for the development of a new class of anti-cancer therapies. Nakajima et al., Experimental Cell Res. 241:126-133, 1998. One mode of action involves the inhibition of one or more classes of histone deacetylases (HDAC).
Histone deacetylase is a metallodeacetylation enzyme having zinc in its active site. Finnin et al., Nature, 401:188-193, 1999. This enzyme is thought to regulate the expression of certain genes by modulating the affinity of acetylated histones for DNA. The acetylation of histones is controlled by the balance between acetylation and deacetylation. The acetylation of histones occurs at a lysine residue of the histone protein. Acetylation of the lysine residue causes the protein to lose some of its positive charge, thereby decreasing its interaction with DNA. Romidepsin has been found to cause the increased acetylation of histones and other regulatory proteins in treated cells. This affects the transcriptional control of various genes involved in cell cycle control, differentiation, and apoptosis. More recently, HDAC inhibitors have been implicated in the control of autophagy.
In addition to romidepsin, various derivatives have been prepared and studied. The following patent and patent applications describe various derivatives of romidepsin: U.S. Pat. No. 6,548,479; WO 05/0209134; WO 05/058298; and WO 06/129105; each of which is incorporated herein by reference.
Given the interest in romidepsin as a pharmaceutical agent, there remains a need for preparing large quantities of highly purified material in a cost effective manner. Various reports of purifying romidepsin from fermentation broth have been reported. U.S. Pat. No. 4,977,138; International PCT Application WO 02/20817; each of which is incorporated herein by reference. For example, WO 02/20817 describes increasing the yield of romidepsin from a fermentation process by the addition of specific amino acids such as L-cysteine to the culture medium. Although such discoveries have provided for improved yields of romidepsin by fermentation, there remains a need for better ways of preparing large quantities of pure romidepsin for research and medicinal use.